In recent years, fuel cell systems which employ, as an energy source, a fuel cell that generates electric power through an electrochemical reaction between a fuel gas and an oxidant gas have been attracting attention. In the fuel cell systems, while a high-pressure fuel gas is supplied from a fuel tank to an anode of a fuel cell, air serving as an oxidant gas is supplied via pressurization to a cathode thereof, and an electrochemical reaction is made to occur between the fuel gas and the oxidant gas, thereby generating an electromotive force.
From among such fuel cell systems, vehicle-mounted fuel cell systems are each mainly constituted by a fuel cell, a secondary battery, a driving motor and an auxiliary apparatus, and are operated by appropriately controlling the power distribution of these components.
Such fuel cell systems include a fuel cell system in which the SOC (remaining capacity) of a secondary battery is controlled to fall within a predetermined range by balancing power required to be generated which is determined based on, e.g., the degree of opening of an accelerator, regenerative power from a driving motor, and power generated from a fuel cell (see, e.g., Patent Document 1).                Patent Document 1: WO2002/015316 pamphlet        